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The Scientist Timeline of DNA

The following is a summary of the scientists and their contributions in the discovery and understanding of DNA. In the McGraw-Hill Ryerson Biology 12 textbook, this pertains to sections 7.1 and 7.2 or pages 218 - 226.

Rami Jadayel

on 7 August 2010

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Transcript of The Scientist Timeline of DNA

Gregor Mendel the Austrian Monk - Patterns of Inheritance in Garden Peas
Maternal and paternal gametes contribute equally to the development of offspring.
Traits are not blended together but rather passed on as "factors of inheritance."
Two factors exist per trait but one, the recessive factor, may not be expressed.
Friedrich Miescher the Swiss Scientist - Discovery of Nucleic Acids
Extracted "nuclein" from the nuclei of white blod cells.
Determined that "nuclein" is composed of:
1. Acidic portion which he coined as "nucleic acid."
11. Alkaline portion, which was determined to be protein Phoebus Levene the Russian Biochemist - the Components of DNA The Scientist Timeline of DNA 1865 1869 1900 - 1930s Distinguished different sugars by their composition:
1. Five-carbon sugar ribose, called "ribose nucleic acid" or ribonucleic acid (RNA).
11. Five-carbon sugar lacking an oxygen, called "deoxyrbiose nucleic acid" or deoxyribonucleic acid (DNA).
Demonstrated that nucleic acids are made up of long chains, a polymer, of nucleotides.
Determined that only four bases differentiated molecules of DNA and RNA.
Concluded that nucleic acids contained equal and recurring amounts of nucleotides, this lead to:
1. Scientists concluding that DNA could not be the material of heredity as it is not complex enough to account for the variation in inherited traits.

In other news... Mendel's factors of inheritence were assosciated with "nuclein."
Determined that "nuclein" made up individual structures called chromosomes.
Resulted in an increase in attention to protein component and properties of nucleic acids. Chromosome 1928 Fred Griffith the British researcher - the Transforming Principle Demonstrated that when heat-killed pathogenic strains were added to a suspension containing a non-pathogenic strain, the non-pathogenic strain transformed to become pathogenic; coined as the transforming principle.
1944 Oswald Avery, Colin MacLeod and Maclyn McCarty - DNA in Cell Function
Performed Griffith's experiments with protein-destroying enzymes as well as DNA-destroying enzymes.
Determined that DNA, and only DNA, was responsible for the transformation of the non-pathogenic bacteria into a pathogenic strain. Oswald Avery Colin MacLeod Maclyn McCarty In a species, the quantity of DNA in somatic cells is constant and double the quantity of DNA in gametes.
The amount of protein varies widely from the cells of one tissue to another and is not necessarily lower in reproductive cells.
1948 Erwin Chargaff the Austrian Biochemist - Chargaff's Rule Determined the following:
1. The four nucleotides were found in varying but characteristic proportions contrary to equal and recurring amounts proposed by Levene.
11. No matter at what age the organisms are, the species that pertain to those organisms will have the same nucleotide composition.
111. In any sample of DNA, the amount of adenine is always equal to the amount of thymine while the amount of cytosine is equal to the amount of guanine; this relationship is known as Chargaff's rule where A = T and C = G. 1952 Alfred Hershey and Martha Chase - the Genetic Structure of Viruses In other news... Alfred Hershey Martha Chase Determined that the transmission of genetic information from the virus to the metabolic machinery of the bacterium could only take place as a result of the injection of DNA into the bacterium.
In other words, when a virus infects a bacterium, it only inserts its DNA and as a result, replicates itself inside. 1953 Rosalind Franklin and Maurice Wilkins - the Helical Structure of DNA Rosalind Franklin Maurice Wilkins Determined the following:
1. By the usage of x-ray imaging, the pattern of shaded areas in Figure 1 indicated that DNA had a helical structure.
11. Hydrophobic nitrogeous bases must be located on the inside while the hydrophilic sugar-phosphate backbone must be located on the outside. Figure 1 James Watson and Francis Crick - the Structural Model of DNA James Watson (left) and Francis Crick (right) Produced a structural model of DNA that could account for all the experimental evidence at hand.
Resulted in a double-helix model after much tampering with the physical model; is now the definitive structure of DNA.
Determined that purines, adenine and guanine, always bonded with pyrimidines, thymine and cytosine.
Determined that the two strands of DNA that make up each double helix are antiparallel; the phosphate bridges run in opposite directions.
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